Contractor Innovation in Thermal Envelope and Firestopping Design This special category of insulation contractor is achieved by a proven record of business activity in these areas: A... Members. 3M Master Contractor What does it mean to be a Certified 3M Trained Master Contractor? In short, it means when we re installing 3M fire protection systems in your building, you... proven ability and commitment to install all passive fire protection applications Factory Mutual Factory Mutual (Approval Standard 4991) was created to evaluate and accredit firestop...